The international standard SAE J1772-2010 provides three methods for charging the electric vehicle: the AC Level 1 charging for slow charging, the AC Level 2 charging and the DC charging for fast charging. The slow charging mainly relies on the charging post and takes more than six hours, so that it is suitable for the electric vehicle which is parked for a long time in the same parking lot. The fast charging is mainly done in the charging station and takes 15 minutes to 2 hours, so that it is suitable for emergency charging of the electric vehicle and daily charging of public vehicles and taxis and at this time the charging power of the electric vehicle is the maximum charging power.
However, there are some problems: the charging for the electric vehicle influences the power grid adversely, such as overload and power loss. Meanwhile, if numerous electric vehicles arrive at one charging station for charging, the electric vehicles in the one charging station will wait for a long time, but there is no electric vehicle waiting for charging in other charging stations.